Post on 10-Jun-2018
Electromagnetic compatibility
of lighting equipment
Common mode chokes for lighting
Application note
Figure 1: Limit values with non-suppressed harmonics of a fixed-frequency switching regulator
[dBµV]
100
80
60
40
20
0
0.01 0.1 1 10 100
Frequency [MHz]
EN 55015, Conducted Emission, QP
CE marking and conformity declaration
In the implementation of the EMC directive, a harmonisation of standards for
lighting technology also ensured that there is a uniform evaluation of EMC in
the European community zone. Lamps and lamp accessories may only be
marketed in the EU if the manufacturer or its agent confirms this evaluation
by an appropriate conformity declaration. Special standards apply with
respect to EMC (electromagnetic compatibility) and interference, and differ
in certain points from the standards for households and industry,
EN 55015
The standard applies to all lighting equipment and its accessories. Excep-
tions apply to equipment operating in ISM (industrial, scientific, medical)
frequency bands, to lighting technology in aircraft and airports and to other
specifically exempted equipment. The limit values for conducted and
radiated interference emission for all other lighting equipment are set forth
there.
The EU decision to finally
abolish incandescent lamps by
2012, the progress in the
luminescent power of light
emitting diodes (LED) and the
further development of
low-pressure and high-pressure
discharge lamps are all leading
to a sharp increase of electronic
modules in lighting technology.
2
Harmonic order Permissible maximum value Permissible value of the
of the harmonic current per harmonic current
[n] W [mA/W] [A]
3 3,4 2,3
5 1,9 1,14
7 1,0 0,77
9 0,5 0,040
11 0,35 0.,33
13–39 3,85/n 0.15 × 15/n
Table 1
Conducted noise emission
The following limits apply to the mains connection:
A quasi-peak (QP) of 110 dBμV is permissible between 9 kHz and 50 kHz.
From 50kHz to 150kHz, the limit value runs linearly to the logarithm of
frequency from 90 to 80dBμV. The limits for QP and average (AV) from 150
kHz and up comply with the generic standard EN 61000-6-3: Emission
standard for residential, commercial and light-industrial environments.
Since the electronics and the illuminant do not always form a unit, and
interferences can therefore also be emitted through the cable to the lighting
means, limit values are also specified for lamp connections. They are QP (AV)
80 (70) dBμV from 150 to 500 kHz and QP (AV) 74 (64) dBμV from 0.5 to 30
MHz. A setup and test with a load emulation of the illuminant are likewise
described. Limit values are defined for control inputs, if the electronics have
them.
Radiated interference emissions
A QP limit value of 30 dB (μV/m) for field-based noise emission applies
between 30 MHz and 230 MHz, and a value of 37 dB applies from 230 to 300
MHz, with a measuring distance of 10m.
EN 61000-3-2
This standard describes the permissible harmonic current emissions for
devices with an input current of up to 16 A per phase. Lighting equipment
and accessories are assigned to class C.
Up to an effective input power of 25 W, the moderate limit values that can be
achieved without a correction of the power factor apply to lighting equip-
ment for discharge lamps (Table 1). For all other lighting equipment (e.g. LED
lamps, ignition and starting devices), no limit vales for harmonics are prescri-
bed up to 25 W.
Alternatively to the limit values of the table 1, it is also sufficient if the third-
order harmonic current does not exceed 86% of the fundamental oscillation
current and the fifth-order harmonic current does not exceed 61%, if the
current flow lasts at least from 60° to 90° and the peak value is reached before
or at 65°.
3
Table 2: * λ is the power factor of the circuit
Harmonic order Permissible maximum value of the
harmonic current in percent of the input
[n] fundamental oscillation current [%]
2 2
3 30 λ *
5 10
7 7
9 5
11–39 3
The following limits apply to devices with an effective input power of >25 W:
The standard permits the use of several operating devices with <25 W in a
lamp with the limit values for <25 W.
EN 61000-3-3
This standard describes the limit values for voltage fluctuations and flicker in
low-voltage supply systems up to 16 A per phase. No limit values apply to
lamps. Lighting fixtures with incandescent lamps up to 1000 W rated power
and lighting fixtures with discharge lamps up to 600 W rated power need
not be tested.
EN 61547
The interference immunity requirements for devices for generic lighting
purposes are established here. The reader is referred to the relevant generic
standards EN 61000-4-x for tests such as electrostatic discharge, HF-EM field,
LF-EM field, burst, surge and voltage dips; the intensity of the tests as well as
the criteria for the various types of lighting devices (e.g. starter units,
discharge lamps, emergency lighting) are set individually.
EMC filters in lighting technology
The objective of the noise-elimination measure is avoid propagation of the
interference currents generated in the electronics. Conducted interference
is primarily emitted via the mains line and the line to the illuminant. For
lighting devices with lager power, the use of IEC power entry modules or
single-phase EMC filters on the mains side is possible.
Figure 2:Block schematic with an EMI filter
4
AC line EMI Filter rectifier
power
electronic
EMI Filter load
lamp
Figure 4:Typical arrangement of a mains filter
The integration of the filters on the circuit board using current-compensated
chokes is advisable for lower powers. The RN series makes the construction
of EMC filters with high power density possible due to the use of toroidal
cores, and has high saturation resistance as well as outstanding thermal
behavior.
RN chokes are less sensitive to electromagnetic coupling than other designs
because of the closed toroidal core and the compact design of the magnetic
circuit.
Mains filter design for lighting technology
The mode of operation of the individual components will be briefly explai-
ned with reference to a typical mains filter. The parasitic capacitances of the
interference source to earth are one propagation path for interference. The
heat sink is a typical example of this for power electronics. The noise currents
flow via the parasitic capacitor to ground and back to the interference
source via the mains lines or other lines. This noise is called common-mode
or asymmetric interference.
To avoid propagation via the mains line, the load-side Y-capacitors in the
filter form a noise sink. At the same time, the impedance of the mains line is
increased by a current-compensated choke. For low power, small parasitic
capacitance to earth or high requirements for leakage currents as in medical
technology, noise elimination with Y-capacitors can also be left out.
The second path for propagating noise is differential mode or symmetrical
interference. The typical source for this is the voltage ripple caused by the
switching process and impedances of parallel components such as capaci-
tors and the circuit path to their terminals.
Figure 3: Current-compensated toroidal core chokes from Schaffner for 0.3 to 10 A
5
P
N
PE
Line
Cx-1 R L Cx-2 Cy
Cy
Load
P‘
N‘
Figure 5: Network emulation with impedance curve
Figure 6:Damping curves of the Schaffner RN143 series
These interferences would mainly propagate via the connected mains
conductors P and N to mains.
The load-side x-capacitor Cx-2) is an interference sink for these noise currents.
With a load-side inductor (PFC choke or DC reacror) the x-capacitor forms a
first low-pass filter and symmetrises the noise level on the two mains lines. The
stray inductance of the current-compensated choke, together with mains-
side capacitor Cx-1, forms another low-pass filter to suppress the propagation
of symmetrical interference to mains.
In general a structure as shown in Figure 4 is sufficient. The requirement for
damping can be found by measuring the module without interference
suppression with the network emulation
As shown in Figure 1, the harmonics of the switching process can exceed the
permissible limit values from EN 55015. The selection of the switching
frequency determines the third, fifth, through n-th harmonics. EN 55105
allows 110 dBuV as the limit up to 50 kHz, and after that the limit value runs
linearly to the logarithm of frequency from 90 to 80 dBμV. It is therefore
advisable to keep the switching frequency below 50 kHz.
For example, if 48 kHz is selected as the switching frequency in consideration
of the bandwidth of the quasipeak measurement, no interference below this
frequency will be caused by the switching process. Thus a value of 110 dBμV
applies to the first harmonic, and then 81 dBμV for the third harmonic at 144
kHz.
If measurement of the non interference-suppressed module containing the
load-side x-capacitor shows that limit values have been exceeded, an appro-
priate preselection can be made based on the damping curves of the RN
choke (see Figure 6).
Line 250 uH 50 uH
2 uF 8 uF 0.47 uF
5Ω 50Ω
EMIReceiver
60
50
40
30
20
10
0
0.01 0.10 1.00 10.00 [MHz]
[Ω]
70
60
50
40
30
20
10
0
10k 100k 1M 10M
dB
RN 143
6
EUT
The rated value for the choke current must be measured for the lowest
possible mains voltage and the largest load case and the highest permissible
temperature under full load. By matching the resonant frequency to the
spectrum of the switching processes, it is possible to damp the third harmo-
nic at 144 kHz by about 70 dB with an RN143-05-02, if that is necessary. The
decisive factor is ultimately the measurement with the network emulator,
however.
Current-compensated chokes for the load and control terminals
In addition to their use as mains filters, current-compensated chokes can also
be used for noise suppression of the load terminal. For ballasts with an
ignition voltage, this level must match the rated voltage of the choke.
For control terminals, RN chokes can not only help suppress the propagation
of interference but can also improve interference immunity in order to meet
the criteria of the interference immunity tests "Fast transients" (EN 61000-4-4)
and "Surge voltages/surge currents" (EN 61000-4-5).
RN chokes – proven quality
The UL-tested RN chokes can be used from 40°C to +125°C, have an MTBF of
>4 million h and meet the requirements for RoHS and REACH.
RN chokes are available from stock anywhere through a world-wide
distribution and sales network:
Inventory
Datasheet
More information on EMC
More information on noise suppression for power electronic modules is
provided by our EMC brochure "Basics in EMC and Power Quality"
Shorform-Catalog
Basics in EMC und Power Quality
For further information visit our website www.schaffner.com or contact
your local Schaffner branch office or the nearest Schaffner partner for
individual consultation.
7
07/2
011e
n
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